Onyango Arnold N, Nakajima Shuhei, Kaneko Takao, Matsuo Mitsuyoshi, Baba Naomichi
Department of Bioresources Chemistry, Faculty of Agriculture, Okayama University, Tsushimanaka, Okayama 700-8530, Japan.
Chem Phys Lipids. 2004 Aug;131(1):81-92. doi: 10.1016/j.chemphyslip.2004.04.004.
Phosphatidylcholines (PCs) having an acyl chain with a 2,4-dienal terminal are expected to be important bioactive compounds formed during lipid peroxidation in vivo. However, they have not been isolated from biological tissues. Here we used electrospray mass spectroscopy to investigate whether a high autoxidative instability may contribute to the difficulty in detecting one such compound, 13-oxo-9,11-tridecadienoyl PC (OTDA-PC, 1). Although we found that pure, synthetic OTDA-PC was very stable, OTDA-PC formed during the decomposition of a PC bearing the 13-hydroperoxide of alpha-linolenic acid (PC-LNA-OOH, 2) was readily converted (i) anaerobically to its corresponding acid PC, 13-carboxy-9,11-tridecadienoyl PC, 3; (ii) aerobically to other bioactive aldehyde (or acid) PC species that have been detected in atherosclerotic tissues. We attribute the high oxidative instability of OTDA-PC to a high vulnerability of its carbonyl hydrogen [H-C(=O)R] to abstraction by lipid-derived radicals, and propose mechanisms for its conversion to the other oxidised PC species (vide supra).
具有2,4 - 二烯醛末端酰基链的磷脂酰胆碱（PCs）有望成为体内脂质过氧化过程中形成的重要生物活性化合物。然而，它们尚未从生物组织中分离出来。在此，我们使用电喷雾质谱法来研究高自氧化不稳定性是否可能导致难以检测到一种这样的化合物，即13 - 氧代 - 9,11 - 十三碳二烯酰PC（OTDA - PC，1）。尽管我们发现纯的合成OTDA - PC非常稳定，但在含有α - 亚麻酸13 - 氢过氧化物的PC（PC - LNA - OOH，2）分解过程中形成的OTDA - PC很容易（i）在无氧条件下转化为其相应的酸性PC，即13 - 羧基 - 9,11 - 十三碳二烯酰PC，3；（ii）在有氧条件下转化为在动脉粥样硬化组织中已检测到的其他生物活性醛（或酸）PC物种。我们将OTDA - PC的高氧化不稳定性归因于其羰基氢[H - C(=O)R]极易被脂质衍生的自由基夺取，并提出了其转化为其他氧化PC物种的机制（见上文）。
